Method for making ferroelectric thin film

Abstract

A ferroelectric thin film comprising at least two stock solutions is made so that the stock solutions are mixed homogeneously in the plane and over the thickness on a substrate, or so that the stock solutions are mixed having a distribution in the plane and over the thickness on the substrate. A ferroelectric thin film mixed homogeneously in the plane is made by discharging two stock solutions 105 and 106 separately at a fixed discharging rate by separate inkjet heads using an inkjet apparatus having at least two inkjet heads, and a ferroelectric thin film mixed homogeneously over the thickness is made by repeating this process. Moreover, a ferroelectric thin film having a distribution of the stock solutions is made by changing the discharging rate in the thickness direction or the in-plane direction.

1 . A method for making a ferroelectric thin film used in a ferroelectric device including a ferroelectric capacitor having an upper electrode, a ferroelectric thin film, and a lower electrode, comprising discharging at least two stock solutions in an inkjetting process through separate inkjet heads of an apparatus having at least two inkjet heads to apply the stock solutions.  
     
     
         2 . A method for making a ferroelectric thin film according to  claim 1 , wherein the stock solutions are a ferroelectric solution and a paraelectric solution.  
     
     
         3 . A method for making a ferroelectric thin film according to  claim 1 , wherein the stock solutions are ferroelectric solutions having different composition ratios.  
     
     
         4 . A method for making a ferroelectric thin film according to any one of  claim 1  to  claim 3 , wherein the discharge amount of each of the stock solutions is changed to generate a distribution of the composition over the thickness of the thin film.  
     
     
         5 . A method for making a ferroelectric thin film according to any one of  claim 1  to  claim 3 , wherein the discharge amount of each of the stock solutions is changed to generate a distribution of the composition in a plane.  
     
     
         6 . A method for making a ferroelectric thin film according to any one of  claim 1  to  claim 3 , wherein a hydrophilic treatment is performed on a substrate before the application of the stock solutions with the inkjetting process.  
     
     
         7 . A method for making a ferroelectric thin film according to any one of  claim 1  to  claim 3 , wherein a water-repelling treatment is performed on a substrate before applying the stock solutions with the inkjetting process.  
     
     
         8 . A method for making a ferroelectric thin film according to any one of  claim 1  to  claim 3 , wherein a discharging time interval in the inkjetting process is set so that a next landing of the stock solution discharged in the inkjetting process occurs sufficiently earlier than drying of the previous landing.  
     
     
         9 . A method for making a ferroelectric thin film according to any one of  claim 1  to  claim 3 , wherein a discharging time interval in the inkjetting process is set so that a next landing of the stock solution discharged in the inkjetting process occurs after the previous landing has completely dried.  
     
     
         10 . A method for making a ferroelectric thin film according to  claim 1  or  claim 2 , wherein the ferroelectric solution and the paraelectric solution are applied so as to each have a distribution in the ferroelectric thin film.